Osteoporosis contributes to decreased bone mass and bone mineral density (BMD) as well as compromised fracture healing rates and bone repair quality. Tissue engineering offers novel strategies to repair large bone defects, but it remains a big challenge in orthopaedic surgery to repair large bone defects, especially in osteoporotic patients. Recently, adipose-derived stem cells (ASCs) were reported to be able to differentiate into the osteogenic lineage. Moreover, ASCs can maintain stable stem cell properties during the aging process, indicating their potential application in bone regeneration in osteoporotic patients. The aim of this study is to evaluate proliferation and osteogenic potential of osteoporotic ASCs in vitro, and the bone regeneration capability of autologous osteo-induced ASCs in poly(lactic-co-glycolic acid) (PLGA) constructs implanted in osteoporotic rat calvarial defects. A total of eighty 6-month-old female Sprague-Dawley rats will be randomly assigned into either the ovariectomy group (n=40) or the sham operation group (n=40). Four months after the operation, the BMD of the entire femur of ten rats in each group will be measured. The rat ASCs from both groups will be cultured in monolayer or three-dimension (3D, seeding ASCs into PLGA mesh) with osteogenic medium (osteo-induced) or growth medium (non-induced) for three weeks. ASC proliferation and osteogenic differentiation will be evaluated using immunofluorescence staining, quantitative ELISA, biochemical assays, and real-time PCR. The remaining thirty rats in each group will have 5-mm-diameter-calvarial-defects created bilaterally. One defect will be randomly implanted with autologous osteo-induced ASC- or non-induced ASC-based premature constructs (n = 15 in each group). PLGA mesh alone implanted in another defect will serve as a control. Six weeks, 12 weeks, and one year post implantation, five rats in each subgroup will be sacrificed and the defect healing will be evaluated using radiodensitometric analysis, BMD measurement, 5CT, H&E and Masson staining, and biomechanical testing. Tracking of ASCs by quantum dots (QDs) labeling will also be performed to confirm the direct role of ASCs during bone regeneration. This study may broaden ASCs' application range in bone tissue engineering and give a bench-to-bedside option for large bone defect repair in osteoporotic patients. PUBLIC HEALTH RELEVANCE: Large bone defects in osteoporotic patients are a big challenge for clinical treatment, in which autologous adipose-derived stem cells (ASCs)-based tissue engineering may be a promising approach due to ASCs unique genetic property. The aim of this study is to evaluate proliferation and osteogenic potential of osteoporotic ASCs in vitro, and the bone regeneration capability of autologous osteo-induced ASCs in poly(lactic-co-glycolic acid) (PLGA) constructs implanted in osteoporotic rat calvarial defects.